The invention relates to a rolling contact bearing with a rotational speed measuring device that uses telemetry from the wheel bearing.
Many rolling contact bearings require a device for detecting their rotational speed. The prior art shows wheel bearings of motor vehicles equipped with rotational speed detection, in order, for example, to derive the speed from the signals obtained and to use this for controlling an anti-lock braking system. These are intended to detect even low rotational speeds, and the sensor has to be positioned at a very small distance from the pulse transmitter wheel or from an encoder disk.
A rolling contact bearing having a pulse transmitter disk that is integrated into the seal between the rings of the bearing is disclosed in DE 37 35 070 A1. However, the sensor has to be arranged with a short air gap with respect to the sealing disk, since the signal strength decreases as the square of the distance.
German Offenlegungsschrift 19 11 513 also discloses a rotational speed measuring device in a rolling contact bearing, wherein the device is integrated into the seal of the bearing. In addition to the air gap problem already mentioned, this has the additional problem that an electrical plug-in connection or a cable has to be provided for the transmission of energy and data. However, both options present a considerable space requirement. In addition, plug-in connections close to the wheel are problematic from the points of view of reliability and being leak tight, and cables permanently fitted to the bearing considerably interfere during handling and installation of the bearing.
U.S. Pat. No. 4,688,951 also discloses a rolling contact bearing in which electric signals are intended to be transmitted without contact. In this case, a sensor arranged on the rotating bearing ring transmits electric signals to a receiver by capacitive or inductive field changes or in the form of radio waves. A battery or a miniature generator supplies the energy to the transmitter. However, this is complicated, susceptible to faults and expensive.